Endoparasitic infection and infestation of homeothermic farm and companion animals are the cause of significant distress and economic loss to pet owners, animal husbandry men and the like. Efficient control of said parasites is, therefore, highly desirable and may be achieved by the administration of suitable endoparasiticidal agents, such as moxidectin and praziquantel.
Moxidectin is a second-generation endectocide of the milbemycin family of macrocyclic lactone compounds. The compound is registered and marketed in various formulations for the control of internal and external parasites in farm livestock and companion animals, including horses. A 2% oral gel formulation (EQUEST, QUEST) for horses is marketed worldwide. The product is highly effective against a broad-spectrum of internal parasites found in horses and ponies.
Equine tapeworms are commonly found in horses throughout the world. Prevalence does not appear to be related to breed or age. The most common species found in surveys has been Anoplocephala perfoliata, with fewer reports involving A. magna and Paranoplocephala mamillana. Until recently the horse tapeworm has been considered to be a relatively harmless inhabitant of the equine gastro-intestinal tract. However, recent research has suggested that heavy burdens may predispose horses to various types of colic, and that the risk increases with the number of tapeworms present.
Moxidectin, in common with other macrocyclic lactones, does not have activity against cestodes, and an alternative class of anthelmintic, such as pyrantel or praziquantel is required for the control of equine tapeworm. Pyrantel is effective when given at double the dose normally recommended for control of G.I. nematodes. Praziquantel is an anthelmintic belonging to the pyrazinoisoquinolene class of compounds. It is effective against cestode and trematode infections in animals and humans. Praziquantel is registered in Australia for the control of tapeworm infections in horses at a dosage of 2.5 mg/kg bodyweight.
Modern endoparasiticidal agents, such as moxidectin and praziquantel, have a wide margin of safety, considerable activity against immature or larval stages of parasites and a broad spectrum of activity. Nonetheless, the usefulness of any endoparasiticidal agent is limited by the inherent efficacy of the drug itself, its mechanism of action, its pharmacokinetic properties, features relating to the host animal, features relating to the target parasites and the form of administration.
The “ideal” endoparasiticidal administrative form should have a broad spectrum of activity against mature and immature parasites, be easy to administer to a large number of animals, have a wide margin of safety, be compatible with other compounds, not require long withholding periods because of residues and be economical. Anthelminthic compositions for equidae are described in U.S. Pat. No. 5,824,653; however, said compositions are limited in their concentration of effective agents, hence requiring multiple doses for efficacious results. Anthelmintic formulations are also described in U.S. Pat. No. 6,165,987; however, these formulations suitable for oral administration are limited to pastes which may make visual identification of contaminants and accurate administration of measured dosages difficult.
Therefore, it is an object of this invention to provide an endoparasiticidal gel composition which is homogeneous and clear and which allows higher concentrations of anthelmintic or parasiticidal agents than formulations known heretofore.
It is another object of this invention to provide a method for the treatment and control of endoparasiticidal infection and infestation in homeothermic animals which gives an earlier onset of protection for a more prolonged period of time in comparison to formulations known heretofore.
These and other features, objects and advantages of the present invention will be apparent to those skilled in the art from the detailed description set forth hereinbelow, and from the appended claims.